High temperature brake disc

ABSTRACT

An annular disc for brakes or clutches in which segmented strips of resin impregnated carbon or graphite cloth are assembled in a partially overlapping relationship with opposite ends of each strip at opposite faces of the disc. The disc is formed and cured under high temperature and pressure to bond the strips together and then pyrolized to produce a carbon or graphite char bond matrix for resisting high temperatures of operation and providing a friction surface composed of the graphite or carbon cloth of the strips and the carbon or graphite binding material between strips.

Wnited States Patent [191 Freeder et a1.

HIGH TEMPERATURE BRAKE DISC Inventors: Herman Freeder; Homer E. Wilt,

both of Akron, Ohio The B. F. Goodrich Company, New York, NY.

Filed: May 12, 1971 Appl. No.: 142,621

[73] Assignee:

US. (31......192/107 M, 188/218 XL, 188/251 A Int. Cl ..Fl6d 11/00 Fieldof Search 192/107 M, 107 R;

188/732, 218 XL, 251 A [56] References Cited UNITED STATES PATENTSJensen ..192/1'07 R Judd ..l92/107 M Bertolet, Jr. ..192/107 M Nitz etal ..192/107 M May 1, revs FOREIGN PATENTS OR APPLICATIONS 478,9749/1936 Great Britain ..192/107 Primary Examiner-Charles J. MyhreAssistant Examiner-Randall Heald Attorney-John D. Haney and W. A. Shira,Jr.

[ 5 7] ABSTRACT An annular disc for brakes or clutches in whichsegmented strips of resin impregnated carbon or graphite 1 cloth areassembled in a partially overlapping relationship with opposite ends ofeach strip at opposite faces of the disc. The disc is formed and curedunder high temperature and pressure to bond the strips together and thenpyrolized to produce a carbon or graphite char bond matrix for resistinghigh temperatures of operation and providing a friction surface composedof the graphite or carbon cloth of the strips and the carbon or graphitebinding material between strips.

4 Claims, 5 Drawing Figures PMENTEQ W 1 1973 3. 7' 3O 3 2 O s 160)HERMAN Z Z bER HOMER E.WILT

v M Y '18 I m.

HIGH TEMPERATURE BRAKE DISC BACKGROUND OF THE INVENTION This inventionrelates to disc type brakes or clutches and particularly to the annularfriction disc members which engage other friction disc members duringoperation of the brake or clutch. These friction disc members arereferred to as the heat sink elements in high energy brakes such asthose used, for example, in aircraft where they must absorb greatquantities of heat and withstand extremely high temperatures during thebraking operation. The friction disc members may have surfaces whichengage friction surfaces on other disc members during the brakingoperation.

It has been found that brake discs made up of pyrolized cloth and resinlaminated in a flat plate or ring will withstand very high temperaturesand have good strength properties. There are other materials such asberyllium which will absorb more heat than the high temperature carbonor graphite brake discs; however, these materials will not withstand thehigh temperatures accommodated by the pyrolized carbon graphiteconstruction. The laminated carbon and graphite discs also have a lowdensity and are therefore able to meet the weight and space requirementsfor aircraft brakes.

With the flat plate laminated carbon or graphite discs, the wear due tofrictional engagement with other discs, was concentrated on the top oroutermost disc and resulted in uneven wearing of these surfaces. As thetop laminated sheet wore through, the bonding material would be exposedand this would further aggravate the uneven nature of the frictionsurface. It was also found that during the fabrication of the discs, thevolatile gases generated during the forming and pyrolization were notalways removed which resulted in gas pockets within the disc whichcreated a weakness in the structure and also caused further unevenwearing and operation of the discs when they were worn down to the areain which the gas pockets were formed. Cost was also a factor whichworked against the use of these discs since the pyrolized cloth fromwhich the sheets are cut is expensive and there was considerable wastein the center and around the edges of the rings cut from the cloth tomake the flat laminated graphite and carbon discs used heretofore.

SUMMARY OF THE INVENTION According to this invention, the brake disc isbuilt up in such a way that the wear is evenly distributed around theface of the disc with the ends of each strip of pyrolized material infrictional engagement with another braking member. Furthermore, as thedisc wears, the ends of the strips wear down exposing new ends whichfurther maintain the even distribution of stress and frictionalengagement around the disc. The bonding material which is also pyrolizedis exposed along with the ends of the strips making up the brake andprovides a mix of materials which can be utilized to obtain the desiredfrictional properties for an applica' tion. The difficulty with gaspockets is also reduced because the gas paths out of the laminatedstructure are increased and of shorter length.

With the construction of this invention the strips of pyrolized materialmay be cut in short segments instead of in the shape of a ring and withthis shape much more of the pyrolized cloth can be used with very littlewaste, thus reducing the cost of the discs.

The accompanying drawings show one preferred form made in accordancewith and embodying this invention and which is representative of howthis invention may be practiced.

BRIEF DESCRIPTION OF THE DRAWINGS In the drawings:

FIG. 1 is a side elevation of an annular disc with some of the laminatedstrips being broken away to illustrate the construction and havinggrooves at the inner diameter for engagement with a 'splined torquetube, the sides of which are represented by the chain-dotted line.

FIG. 2 is a sectional view of the disc taken along the plane of line 22of FIG. 1.

FIG. 3 is a plan view of a sheet of pyrolized cloth showing how thestrips are cut from the sheet.

FIG. 4 is an enlarged sectional view of a portion of the disc duringconstruction showing how the strips are laid up in partially overlappingcondition.

FIG. 5 is an enlarged fragmentary sectional view taken along the planeof line 5-5 of FIG. 1.

DETAILED DESCRIPTION Referring to FIGS. 1 and 2, a high temperature discassembly 10 is shown in the completed condition having grooves 11 forengagement with splines 12 of a torque tube 13 which may be part of abrake structure, not shown. The disc assembly 10 is shown here as astator; however, it is understood that it may also be used as a rotorwith the grooves at the outer diameter for en-' gagement with a rotatingpart. The disc assembly 10 is an annular body having flat parallel faces14 and 15 at opposite sides thereof for frictional engagement with otherdiscs or brake parts, not shown. The disc assembly in its finishedcondition is a unitary annular body of pyrolized carbon or graphitematerial which is built up from a plurality of segmental strips 16bonded together by a char bond 17 which is shown more clearly in FIG. 5.

To better understand the construction, the preferred method ofmanufacturing the disc assembly 10 is set forth. As shown in FIG. 3, asheet 18 of pyrolized cloth is shown which is chosen for the finalproperties desired and this usually is a function of the carbon contentof the fabric. Although several different materials may be used, it hasbeen found that rayon is satisfactory for this application. The sheet 18may be of either graphite cloth or carbon cloth depending upon thedegree of pyrolization. The process for making this material is wellknown in the art and therefore it will not be described here. The fabricof the sheet 18 has been impregnated with a high temperaturethermosetting resin 19 or other bonding material such as phenolic shownmore clearly in FIG. 4. This resin material 19 is chosen for its abilityto convert into carbon or graphite upon pyrolization during a later stepin the manufacture of the disc assembly 10.

The strips 16 are in the form of segmental members having curved sides22 and 23 at the inner and outer diameters respectively. The strip 16may extend circumferentially in an arc preferably from 45 to and in thisparticular case, the angle A, shown in FIGS.

1 and 3, is 90 indicating a strip having a circumferential lengthencompassing an arc of 90. It is understood that other lengths from to45 and over 180 may also be used for some applications. In theembodiment shown, the strips 16a, 16b, 16c and 16d may be cut out of thesheet 18 with a minimum of waste material by nesting the strips togetherwith the curved sides 22 at the outer diameter next to the curved sides23 at the inner diameter.

After the strips 16 are cut from the sheet 18, they are laid up in apartially overlapping condition, as shown in FIG. 4. Each of the strips16 has ends 24 and 25 which extend into the faces 14 and 15 respectivelyof the disc assembly and, as shown in FIG. 1, by continuing theoverlapping lay-up of the strips an annular configuration is obtained.

As shown in FIG. 3, the sheet 18 of pyrolized cloth may have cords 26constituting the warp of the cloth which extend in a directiontangential to the curved side 22 of the strips 16 at a midpoint M. Thisprovides for greater strength in the peripheral direction for the discassembly shown in this embodiment. It is understood that for otherstrength requirements the cords 26 may be at different angles and thestrips 16 may be assembled with the cords 26 crossing at an angle toprovide balanced strength characteristics for particular applicationswhere the stresses on the disc assembly are more severe in otherdirections.

After the strips 16 have been laid up in the annular configuration,shown in FIGS. 1 and 4, the disc 10 is subjected to high pressures andhigh temperatures in an autoclave or hydraulic press where thethermosetting resin 19 is cured. The disc assembly 10 is then removedand any glaze on the surfaces is removed by a vapor or grit blast toopen the microscopic holes in the surface providing for passage of gasfrom the disc assembly which may then be placed in another heater oroven at a temperature slightly above the cure temperature for furthercuring of the resin 19 and removal of the residual gases from the discassembly. With the overlapping laid-up construction of this inventionthere are shorter passages leading to the faces 14 and as well as to theinner diameter and outer diameter through which the gases may pass.After this postcure operation, the disc assembly 10 is pyrolized atwhich time the resin 19 is converted to a char bond 17 of graphite at ahigher temperature such as 2,800 C. or to carbon at a lower temperaturesuch as l,400 C. This operation is done in a controlled atmosphere andin a manner well known in the art.

The disc assembly 10 may then be subjected to a filling process duringwhich gas or resin is forced into the disc assembly through themicroscopic openings and gas paths to build up deposits within theassembly which may be converted to carbon or graphite. The disc assembly10 is then slowly cooled under controlled conditions to prevent anytemperature shock to the material of the assembly. Following thisoperation, the disc assembly 10 may be machined giving it a final smoothshape, as shown in FIG. 1, with grooves 11 at the desired positions.

As shown in FIGS. 1 and 5, the resin material 19 which has beenpyrolized forms the char bond 17 between the strips 16 and this may beof carbon or graphite as explained heretofore. The faces 14 and 15 aremade up of the exposed ends 24 and 25 of the strips 16 and of theexposed faces 27 and 28 of the char bond 17. This provides for animproved and constant friction surface throughout the wear life withbalanced physical properties. The type of surface at the faces 14 and 15can be manufactured for the service requirements of the brake or clutch.For example, the exposed ends 24 and 25 of the strips 16 may be eitherof carbon or graphite depending upon whether the sheet of pyrolizedcloth 18 from which they are cut is a graphite cloth or carbon cloth.Furthermore, the char bond faces 27 and 28 may be either of graphite orcarbon depending upon the temperature at which the disc assembly 10 ispyrolized.

In operation of this disc assembly, the faces 14 and 15 are infrictional engagement with other brake parts and the surfaces 24 and 25of the strips 16 and the surfaces 27 and 28 of the char bond 17 will beworn down; however, as this occurs the surfaces of adjacent portions ofthe strips 16 and char bond 17 will be exposed providing a uniformfrictional surface at all times with a brake construction which issuitable for operation in the 2,000 F. to 3,500 F. operation range. Thisis done with a construction which is structurally sound and relativelyeconomical to manufacture.

We, therefore, particularly point out and distinctly claim as ourinvention:

1. A high temperature disc for a brake or clutch comprising an annularbody having parallel faces and a plurality of partially overlappingstrips of carbon cloth bonded together by pyrolized resin disposedbetween said overlapping strips, each of said strips extendingcircumferentially of said disc from one to the other of said faces withone end of each of said strips and said pyrolized resin forming aportion of said one of said faces and the other end of each of saidstrips and said pyrolized resin forming a portion of said other of saidfaces whereby the optimum proportion of carbon cloth and pyrolized resinmay be provided as said parallel faces wear and the ends of said stripsare worn progressively exposing adjacent portions of the overlappedstrips and pyrolized resin for frictional engagement with another brakepart.

2. A high temperature disc for a brake or clutch comprising an annularbody having parallel faces and a plurality of partially overlappingstrips of high temperature pyrolized material bonded together by apyrolized bonding material disposed between said overlapping strips,each of said strips extending circumferentially of said disc from one tothe other of said faces with one end of each of said strips of pyrolizedmaterial and said pyrolized bonding material forming a portion of saidone of said faces and the other end of each of said strips and saidbonding material forming a portion of said other of said faces wherebythe optimum proportion of high temperature material and bonding materialmay be provided as said parallel faces wear and the ends of said stripsare worn progressively exposing adjacent portions of the overlappedstrips and bonding material for frictional engagement with another brakepart.

3. A high temperature disc according to claim 2 wherein said pyrolizedbonding material consists of a pyrolized resin.

4. A high temperature disc according to claim 2 wherein said hightemperature pyrolized material consists of carbon cloth.

2. A high temperature disc for a brake or clutch comprising an annular body having parallel faces and a plurality of partially overlapping strips of high temperature pyrolized material bonded together by a pyrolized bonding material disposed between said overlapping strips, each of said strips extending circumferentially of said disc from one to the other of said faces with one end of each of said strips of pyrolized material and said pyrolized bonding material forming a portion of said one of said faces and the other end of each of said strips and said bonding material forming a portion of said other of said faces whereby the optimum proportion of high temperature material and bonding material may be provided as said parallel faces wear and the ends of said strips are worn progressively exposing adjacent portions of the overlapped strips and bonding material for frictional engagement with another brake part.
 3. A high temperature disc according to claim 2 wherein said pyrolized bonding material consists of a pyrolized resin.
 4. A high temperature disc according to claim 2 wherein said high temperature pyrolized material consists of carbon cloth. 